Re: [Xen-devel] [PATCH v2] pci: clear {host/guest}_maskall field on assign

[Jan Beulich <jbeulich@xxxxxxxx>]

On 09.10.2019 10:33, Roger Pau Monne wrote:
> The current implementation of host_maskall makes it sticky across
> assign and deassign calls, which means that once a guest forces Xen to
> set host_maskall the maskall bit is not going to be cleared until a
> call to PHYSDEVOP_prepare_msix is performed. Such call however
> shouldn't be part of the normal flow when doing PCI passthrough, and
> hence the flag needs to be cleared when assigning in order to prevent
> host_maskall being carried over from previous assignations.
> 
> Note that the entry maskbit is reset when the msix capability is
> initialized, and the guest_maskall field is also cleared so that the
> hardware value matches Xen's internal state (hardware maskall =
> host_maskall | guest_maskall).
> 
> Also note that doing the reset of host_maskall there would allow the
> guest to reset such field by enabling and disabling MSIX, which is not
> intended.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

I'm also Cc-ing Jürgen for a possible release ack for 4.13, but
I'd also like to point out that I'd prefer to wait a little with
committing this to get at least one Tested-by.

Jan

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